Types Of Soil Structure Research Articles

Analisa Prediksi Potensi Likuifaksi di Kota Rengat Kabupaten Indragiri Hulu

The number of incidents occurring on the island of Sumatra, especially West Sumatera and Jambi provinces that affect the vibration of the earthquake in Rengat City on a large scale can lead to the movement of land such as landslides and stagnant ground water sources can lead to liquefaction. The purpose of this research is to know how the arrangement of soil type at research location Rengat City and to know the location reviewed in Rengat City, and its surrounding experience potential liquefaction based on some existing penetration test data. This research was conducted to predict liquefaction potential that occurred in Rengat City of Indragiri Hulu Regency with secondary data of penetration test of konus with Seed and Idriss method (1971). The calculation of potential liquefaction prediction is done by determining the number of soil layers, estimating the weight of the soil volume, determining the soil overburden, determining the effective soil stress, determining the corrected confront resistance, calculating Cyclic Strees Ratio (CSR), calculating Cyclic Resistance Ratio (CRR). After calculating the value of Magnitude Scalling Factor (MSF) and calculating the value of safe factor by comparing the value of Cyclic Strees Ratio (CSR) with Cyclic Resistance Ratio (CRR) if the calculation <1 factor is safe then potentially liquefaction occurs. Based on the results of the analysis of the 7 locations with a total of 2 cone penetration test conus analyzed in this study in Rengat City, obtained the type of soil structure is not uniform and based on the results of analysis, from the 7 research sites with tottal 21 point penetration test konus reviewed at magnitude 5 to 10 in Rengat City Indragiri Hulu Regency. In the type of sand soil in the dominant study area can not be achieved liquefaction, this is reinforced from the calculation (SF)> 1 safe factor (SF: 1.0).

Evolution process of the microstructure of saline soil with different compaction degrees during freeze-thaw cycles

For backfill projects in seasonally frozen regions, freeze-thaw and compaction are two critical factors that affect engineering safety by changing the soil structure. This study investigated the effects of freeze-thaw cycles on the microstructure characteristics of saline soil with different compaction degrees using mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM), and laser particle size analysis (LPSA). The compacted soil samples show a bimodal pore size distribution (PSD). With an increase in the freeze-thaw cycles, the volume of intra-aggregate pores (<4 μm) gradually decreases, while that of inter-aggregate pores (>4 μm) varies with the density of soil samples. Furthermore, compaction has a decisive effect on the volume of inter-aggregate pores. Under the effect of freeze-thaw cycles, the void ratio of the low-density soil sample decreases, and the soil structure gradually becomes denser, showing thaw settlement deformation. However, in the high-density soil sample, the void ratio increases and the soil structure becomes loose, showing frost heaving deformation. Moreover, the freeze-thaw cycle also leads to the breakage of coarse particles and the aggregation of fine particles. Correspondingly, the soil structure type changes from a flocculent structure to a granular stacked structure and then to a cemented-aggregated structure. After 60 freeze-thaw cycles, the cracks are penetrated and the water migration channels are formed, the soil structures all reach a new equilibrium state. Meanwhile, the void ratios of different compacted soil samples are close to the same residual value. Test results suggest that there may be an optimal compaction degree between 90% and 95%, where the soil microstructure is least affected by freeze-thaw cycles. This study may provide theoretical guidance for the construction of backfill engineering projects in seasonally frozen regions from a micro-perspective.

Response of surface evaporation and subsurface leakage to precipitation for simulated epikarst with different rock–soil structures

Karst water is an extremely important resource and can respond to precipitation events quickly due to the high rock exposure rate, shallow and uneven soil layers, and various crack sizes. The impacts of this special rock–soil structure type on hydrological processes are difficult to quantify,mainlybecause the karst subsurface structure is very complex. In this study, lysimeters representing four rock–soil structures with two rock exposure rates (50% and 80%) and two soil thicknesses (5 cm and 20 cm) were constructed at the Puding Karst Ecosystem Research Station, Chinese Academy of Sciences. The following results were obtained by observing the evaporation and leakage from September 2019 to August 2020. 1) Over a year, the evaporation of the 80% rock exposure lysimeter was approximately 8% less than that of the 50% rock exposure lysimeter, while the two lysimeters with different soil thicknesses had only a 2% difference in evaporation. 2) The surface evaporation of different rock exposure rates varies greatly after different rainfall intensities. However, there was no significant change in surface evaporation between different soil thicknesses after rainfall of different intensities. 3) Generally, with the increase in the rock exposure rate, the infiltration coefficient nonlinearly increased. The leakage coefficients for cracks of different sizes and different soil thicknesses were approximately 0.67 and 0.57, respectively. 4) The amount of leakage and the time to reach the peak flow varied greatly among different rock–soil structures and were also affected by the antecedent rainfall. Thus, rock exposure has a great impact on surface evaporation after rainfall, and the influence of cracks on subsurface hydrological processes was greater than that of soil thickness. These findings can provide a scientific reference for water use and management practices in karst areas.

Estimating the overconsolidation ratio in uniform cohesive soil with cone penetrometer tests considering soil structure and index properties

A basic empirical approach to estimate the preconsolidation stress and overconsolidation ratio, OCR, in uniform cohesive soils using cone penetration and piezocone tests uses a correlation factor, kc, that is equal to the preconsolidation stress divided by the net tip stress referenced to the soil plasticity index. An adaptation of the “stress history and normalized soil engineering properties” (SHANSEP) format extends this basic approach by organizing the data into normally consolidated and overconsolidated components. The SHANSEP-based approach is improved in this paper by applying an empirical method to identify structured and unstructured soil behavior and to develop a separate empirical correlation for each type of soil structure. Overconsolidated structured soils are shown to exhibit kc values less than the normally consolidated kc and the m exponent in the SHANSEP relationship is greater than 1. In unstructured overconsolidated soils, the kc value is greater than the normally consolidated kc value and the SHANSEP m exponent is less than 1. The proposed method to identify structured vs. unstructured behavior is an important improvement in the approach and helps illustrate why some mCPTu values are less than 1 and others are greater than 1. Site characterization efforts are significantly improved when structured soil behavior is identified and included in the assessment of OCR.

An in situ method for quantifying tillage effects on soil structure using multistripe laser triangulation

Soil structure is an important physical property that can be degraded by soil tillage, but methods for quantifying soil structure are both few and time consuming. We developed a method for multistripe laser triangulation (MLT) scanning to quantify soil structure that can be accomplished quickly (15 min of scanning per A horizon exposure) in the field. We scanned three soil pits to a depth of 30 cm in three fields under conventional tillage (CT), three under no-till (NT) and three under perennial grass (PG). For both 0- to 10- and 0- to 30-cm pit depths, we calculated the Dirichlet tessellation area variability (DTAV) for each pit. We found the DTAV from 0- to 10-cm depths was sensitive to tillage type (p = 0.09) and clay percentage (p = 0.06), while the 0- to 30-cm depths were sensitive to neither. Specifically, CT fields had significantly higher 0- to 10-cm DTAVs than NT (p = 0.06) and PG (p = 0.07) fields, while NT and PG were not different from one another (p = 0.99). The information carried by the DTAV may be thought of as the regularity of the Dirichlet tessellation feature areas, which is driven by the regularity of observable soil structural units in the field. The DTAV was not significantly related to soil structure type, grade, or class size described in the field. The DTAV provides an alternative or complement to field soil descriptions that is quick, repeatable, objective, and sensitive to changes in soil structure in response to tillage practice.

Testing of Subsoil Support in Physical Model of Piled Embankment

Abstract Piled embankment is a type of soil structure that offers convenient technical and cost effective solution for the construction of transport lines in situations when soft soils are present, groundwater is near to surface, or there is an organic unbearable soil profile of significant depth. Other reasons for using pile support for embankment is that total replacement of soft soil is not a cost effective solution or that any other ground improvement techniques are not efficient enough. The article describes continuation of research on pile embankment structure design and its verification by a physical model. Partial support of subsoil and load transfer can be considered in piled embankment structure at some cases of subsoil type. Partial support means that the calculated tensile forces induced in reinforcement on pile heads are lower compared to the case of a very soft subsoil (without subsoil support). After a series of tests of physical models of piled embankments without subsoil support, new models with subsoil support have been prepared. There are many possibilities of simulating soft subsoil, our team decided to use mattress foam which has a non-linear stiffness and this material is convenient for the installation. A foam type was selected to simulate partial soil support for which basic parameters were determined for further research.

Relationship between soil water retention model parameters and structure stability

Studying and modeling the effects of soil properties and management on soil structure and near saturation water retention is vital for the development of effective soil and water conservation practices. The contribution of soil intrinsic properties and extrinsic conditions to structure stability was inferred, in quantitative terms, from changes in water retention curves near saturation (low matric potential, 0-50 cm, macropores > 60 µm) that were obtained by the high energy moisture characteristic (HEMC) method. The S-shaped water retention curves were characterized by the modified van Genuchten model that provided: (i) the model parameters α and n, which represent the location of the inflection point and the steepness of the water retention curve, respectively; and (ii) the soil structure index, SI=VDP/MS, where VDP is the volume of drainable pores, and MS is the modal suction. Model parameters, claculated by the soil-HEMC model, were related to soil properties and hence soil water retention properties were linked to measured characteristics in several field and laboratory experiments. Soil SI increased exponentially with the increase in α and the decrease in n, while the relationship between SI and α/n was linear. An improved description of the water retention and its link to pore and apparent aggregate size distribution, by using the model parameters α and n, could potentially assist in the selection of management practices for obtaining the most suitable type of soil structure depending on the desired soil function.

Comparison of three models describing bromide transport affected by different soil structure types

This study was conducted to investigate the effects of soil structure on bromide (Br) transport through three soils with granular, prismatic, and single-grain structures. The breakthrough curve (BTC) of the single-grain structure was sigmoidal, symmetrical and similar to a piston flow, showing the dominance of mass flow. In contrast, the BTCs of the granular and prismatic structures were initially steep, becoming more gradual at high pore volumes (PVs). The stable structure and preferential pathways caused the early breakthrough of Br in the leachate of these columns. The convection–dispersion equation (CDE), mobile–immobile water (MIM), and dual-permeability (DP) models were fitted to observed data using the program HYDRUS-1D. The equilibrium transport model (CDE) was not as successful as non-equilibrium (MIM and DP) models in describing the Br transport in prismatic and granular soil columns, although it was able to describe the Br transport in single-grain column well. Overall, the results demonstrated the importance of soil structure in pollutant transport through soils.

Morfologia e propriedades físicas de solo segundo sistemas de manejo em culturas anuais

Qualidade física do solo é sua capacidade de sustentar o pleno desenvolvimento das plantas. O objetivo deste trabalho foi estudar diferentes sistemas de semeadura direta para a produção de grãos em áreas de agricultura familiar sob Latossolo Vermelho no norte do Paraná, Brasil, através do estudo da morfologia e de algumas propriedades físicas do solo. O estudo foi baseado na descrição da estrutura de solo de perfis culturais em áreas cultivadas com lavouras anuais sob diferentes sistemas de manejo de solo (semeadura direta com e sem rotação de culturas, semeadura direta com escarificação eventual e o cultivo mínimo). Concomitantemente à descrição dos perfis foi determinada a resistência do solo a penetração, a densidade do solo, a umidade do solo e o grau de floculação da argila. Cada manejo estudado foi caracterizado por um tipo de estrutura de solo a qualse correlacionou com os valores de resistência, densidade e grau de floculação e em todos os manejos estudados abaixo dos 0,30 m, os perfis analisados apresentavam condições estruturais satisfatórias ao desenvolvimento radicular.

Chapter 8 Engineering behaviour of desert soils

Whilst a wide range of soils and rocks may be encountered in desert areas, hot desert soils are typically characterized by: Engineering works will generally lead to changes in stress or changes in moisture content in the ground, and this chapter outlines the soil mechanics frameworks that allow the response to these changes to be assessed. In arid environments, wetting of the soil from its natural dry state is a common result of construction activity and urban development. Ground movements caused by swelling or collapse of the soil may result. These movements can be relatively large and are often more significant than those resulting from a change in total stress. The arid conditions allow soluble salts to remain in the soil, and they are thus encountered at depths and at concentrations not normally found in wetter environments. If the equilibrium is altered by changes in the groundwater regime, ingress of water or in the amount of evaporation at the ground surface, then leaching or precipitation of salts may lead to volume changes or changes in strength and/or stiffness of the ground. Salts may also change from anhydrous to hydrated forms (or vice versa) with consequential volume changes and associated ground movements. All of these characteristics may be present in a given soil, which could, for example, be partially saturated and weakly cemented by soluble salts, and expand when wetted at low stress but collapse when wetted under higher stresses. The engineering behaviour of these soils can be understood in the context of partially saturated soil mechanics, with consideration given to factors specific to arid environments such as particular types of soil structure and the common occurrence of salts. However, although research in universities and companies …

Effects of soil structure on soil behaviour: Illustrated with loess, glacially loaded clay and simulated flaser bedding examples

Soil structure is considered to be a systematic homogeneously repetitive heterogeneity of properties and conditions of soil. For upscaling and homogenisation of properties and conditions it is necessary to understand the ways in which soil structures occur, and to obtain understanding of the ways in which it influences soil behaviour. Using three case studies, different aspects of the effects of soil structure in soil mechanics are discussed. The very loose grain scale packing of loess deposits, held together by weak structural bonds between particles, results in dramatic propagating failure when the strength of the bonds is exceeded by deformations, as illustrated in the first case. Nonhorizontal stresses induced in the subsurface below moving continental ice sheets result in rotated stress fields within the affected soil. The rotated stress field is stored in the structure of the soil, as is shown in the second case, and influences present day properties and behaviour of these clays. It is shown in the third case that there is a large difference in the behaviour of clayey sand depending on whether the clay occurs in the form of the common clay flasers or whether the clay is homogeneously dispersed in the sand. The deformation and stress propagation in the case of sand with clay flasers results in local failures and shear planes due to the large contrast in the properties of the materials making up the sedimentary structure. The result is that many of the properties of sand with flasers are rather more like the clay of the flasers than the sand. Incorporation in the engineering practice of effects of common types of soil structure is made possible with the widespread availability of techniques such as numerical modelling. These techniques enable the development of appropriate tools for practical application.

RELATIONSHIPS BETWEEN SOIL COLOUR, SOIL STRUCTURE AND SOME SOIL PROPERTIES IN BEYŞEHİR WATERSHED

This study was carried out to investigate relationships amoung soil colour, soil structure, and soil texture, organic matter contains, total lime contents, soil reaction in Beysehir Watershed. The soil colour values descripe based on Munsell soil color scala. It was used interspecific correlation analysis as statistical methot in the study . According to the results of the statistical analysis, it was found important relationships between soil colour class and soil structure types and the units of organic matter contents and total lime contents. It is important to evaluate mainrock and climate species in terms of evalation to relationships soil structure and soil physical and chemical species. First of all, it may be the most important things that National Soil Color Scala is development for Turkiye. Keywords: Soil colour, Soil structure, Interspecific correlation analysis

Efficient ground grid designs in layered soils

A detailed analysis of the effects of ground grid configuration on grounding performance has been carried out for uniform and horizontally stratified soils with multiple layers. The results of the analysis reveal that the most efficient and cost-effective design is highly dependent on soil structure type and characteristics. In the absence of ground rods, grounding grids with uniform mesh size are quite efficient in soils having a thin (relative to grid size) high resistivity (relative to the lower layers) top soil, while grids with small mesh size at the periphery of the grid provide optimum performance in uniform soils and soils with low resistivity top soils. Ground rods were found to be effective only when a significant portion of their length is in contact with a low resistivity soil, as expected.

Time aggregation of nitrogen leaching in relation to critical threshold values

Leaching of nitrate contributes to the deterioration of groundwater and can consequently have a negative influence on the quality of our drinking water. Critical threshold values for nitrogen leaching are established to preserve groundwater quality. A critical threshold value for nitrate leaching of 50 mg l −1 (11.3 mg N l −1), similar to the drinking water standard, serves as a threshold value for European countries. However, the temporal aggregation scale on which this threshold value should be considered is unknown. A well tested simulation model was used to evaluate the exceedance of the threshold value at different time aggregation levels, ranging from one day till 30 yr. For three different soil structure types within one soil type and a selected fertilisation regime, the aggregated nitrogen leaching over 30 yr was 11.4, 19.2 and 10.6 mg l −1. Considering an aggregation level of one day, the critical threshold value of 11.3 mg N l −1 was exceeded 2973, 5801 and 2556 times, respectively, for the three structure types during 30 yr. By considering other time aggregation levels, a clear relation resulted between time aggregation level and the number of time elements during which the critical level was exceeded. Results strongly indicate that a critical threshold value for leaching should include an associated time-aggregation level.

Fractal dimensions for volume and surface of interaggregate pores — scale effects

Geometrical attributes of pore systems in soil have shown fractal scaling. Scaling in natural materials is inherently statistical, i.e., fractal dimensions may change with scale. While fractal dimensions characterizing pore surface roughness, D s, or scaling of pore sizes, D v, have been reported, seldom are both measurements made at more than one scale. We examine a scale effect on D v and D s values, and relationships between fractal dimensions of both properties. Natural and artificial types of soil structure were studied in a Normania soil. Natural soil structure was sampled from experiments involving: (l) three primary tillage tools, sampled immediately after tillage; and (2) three tillage systems, sampled after consolidation. Artificial soil structure was formed in columns packed with aggregate assemblies that included two single aggregate-size fractions, and two mixtures of six aggregate-size fractions (each covering two ranges) made to obtain fractal aggregate-size distributions. Block-like samples from all sources were resin-impregnated in situ and a face was cut and polished. Images of UV-illuminated faces were obtained at three magnifications and then pooled into two groups. A box-counting technique was applied to area and outline of pores to obtain D v-box, and D s-box, respectively; D s was also calculated from area-perimeter relations ( D s- AP ). Box-count data showed two segments; D v-box and D s-box were evaluated in relation to each segment and to D s- AP . Coefficients of determination in the relation D s- AP vs D s-box were relatively low, indicating discrepancies between the two methods. Fractal dimensions were not scale-invariant. Values of D s-box for aggregate assemblies decreased with resolution, especially for single aggregate-size fractions. Values of D v-box were more influenced by aggregate size than resolution. Both D s-box and D v-box varied with resolution for freshly tilled soil. For somewhat consolidated soil, variations in values of both fractal dimensions were related to tillage systems. Values of D s-box and D v-box were highly correlated, with linear relations depending on magnification and type of soil structure.

Classifying soil structure using neural networks

Various feed forward artificial neural networks (ANNs) with back propagation were tested to classify 3 types of soil structure (granular, blocky, and massive) from 390 soil samples. The samples represented soils falling within the Ustoll taxonomic suborder that are part of the National Cooperative Soil Survey (USDA, NRCS) data base. The best network found to predict soil structure was one with 3 input nodes, 2 hidden nodes, and 3 output nodes with accuracies on the order of 79%. Inputs were percent organic carbon, silt, and clay. Simple perceptrons and simple linear perceptrons, e.g. networks with no hidden nodes (3 å 3), had accuracies of only 46%. Thus, ANNs are capable of learning soil structure from soil characterization data, and show a greater ability to classify soil structure types than simpler, linear methods. Classification of soil structure from commonly measured quantitative soil parameters is important because of the role structure plays in determining other soil properties, making it a critical component for modeling the soil system. This study shows the potential of artificial neural networks to recognize and learn complex relationships between quantitative soil parameters that can be used to correctly classify soil structure, and allow soil characterization data to be more effectively used for modeling activities.

Wuchsformen bei Arachis hypogaea L.

The growth forms of Arachis hypogaea L. subsp. hypogaea var. hypogaea cv. ‘Florman INTA’ and A. hypogaea L. subsp. fastigiata Waldron var. fastigiata cv. ‘Colorado irradiado INTA’ were studied. Growth forms of plants taken in the same type of soil structure which had been treated with different soil management practices were compared. Both cultivars were planted into two different land plots, one of them with a normal soil profile and the other one with a soil cover ranging from 8 to 18 cm in depth. Samples of serial and subterranean parts were collected every other 10 days. Their dry weight was determined. Rain fall during the cycle was recorded.Growth forms of the two cultivars were compared since sowing to harvest time within each tested plot. Plants from hard layer soil developed certain characteristics. Internodes were found to be shortened. Decreasing number of reproductive branches with lower number of flowers in each branch was observed. A lower dry weight percentage per plant was measured. Root systems showed smaller volume. Directional growth changes in tap roots occurred and xylem tissue showed some abnormalities.

Simulation modelling as a method to study land qualities and crop productivity related to soil structure differences

Research on soil biota under natural conditions in the field is complicated because large fluctuations in populations of certain species may occur as a result or natural or man-induced fluctuations in soil physical and chemical conditions. As a result, many experiments have therefore been made in the laboratory under controlled conditions. Though quite valuable, such data may be difficult to extrapolate to field conditions. To better relate biotic data to physical and chemical conditions in the field, expensive long-term monitoring programs can be initiated to collect both types of data. Physical, and chemical processes in soils can also be characterized by simulation techniques. Simulation requires one-time measurement of some basic and characteristic soil parameters, such as hydraulic conductivity and moisture retention, which are used in a model that calculates water contents in the soil at any given depth and time as a function of precipitation, evaporation and water table levels. Simulation modelling has been applied successfully to calculate water regimes in the soil, for periods of many years. The technique would appear to be particularly appropriate for use in a dynamic physical characterization of different types of soil structure, formed by various soil biota. Results are presented of a study in a sandy loam soil in the Netherlands with biogenic structures in grassland and a more compact physicogenic structure in arable land. Measured hydraulic conductivity and moisture retention data, and their variability were used in a simulation model to calculate important land qualities for a thirty year.period. Land qualities were expressed in stochastic terms by focusing on the probability that certain water and associated air contents and trafficabilities would occur at any given data. Results also reflected the effects of variability of input data. Exploratory modelling was used in this study to estimate effects of an increase of the hydraulic conductivity (which might result from an increase of biological activity), on water and air contents in the soil during the year.

Impact of soil management systems on soil structure and physical properties in a clay loam soil, and the simulated effects on water deficits, soil aeration and workability

The effects of different soil management systems on soil structure and associated physical properties in a Dutch clay loam soil were evaluated using a combination of simulation modelling, field investigations and laboratory experiments. The investigations were focused on field recognition of identical soils only differing in structure type caused by soil management systems. Two soil structure types were recognised: a type developed in permanent grassland and a type in young arable land, which had been used for intensive vegetable growing since 1979. The types were characterised by examining the micro- and macro-morphology and soil hydraulic properties, such as soil structure, rooting patterns, pore shape and size distribution, bypass flow and water retention and unsaturated hydraulic conductivity characteristics. Field recognition of structure types and subsequent morphological and physical characterisation was used as an alternative to the application of a machine-soil submodel. Significantly different properties of both soil structure types were functionally interpreted by using a simulation model for the soil-plant subsystem. Morphological and hydraulic analyses were essential for the definition of proper boundary conditions and input parameters. The land qualities water deficits, workability and soil aeration were calculated for a potato crop under Dutch climatological conditions. Expressions for temporal variability were obtained by using a 30 year record of weather data. The soil structure of permanent grassland proved to be more favourable than that of young arable land. This resulted in a 10% decrease in the average annual water deficit, 40% more workable days in the planting phase and 5–10% more days with a well-aerated soil. The impact of these differences on the potato tuber yield interpreted in terms of the effect of soil structure degradation, was estimated to be at least 5% in 20 out of 100 years under Dutch climatic conditions. The differences calculated also equalled the maximum possible effect of soil structure regeneration.

Advances in characterization of soil structure

Soil structure is defined as “the spatial heterogeneity of the different components or properties of soil”. Aspects of soil structure which are important for plant development, soil water balance and soil workability are reviewed briefly. The different types of soil structure which occur on different size scales are placed in a hierarchical order. Different mechanisms give rise to the different hierarchical orders. Similarly, different physical/chemical/biological processes are involved in the stabilization of the different hierarchical orders. A number of methods for measuring soil structure are described. Preference is given to methods involving direct observation of structural features by scanning electron microscopy and by optical scanning of impregnated sections and fracture surfaces. These need to be supported by assessments of the stabilities of compound particles in water and of the mechanical strengths of compound particles as a function of water content. “Good” soil structure is described as one where all the hierarchical orders are well-developed and stable. The greatest lack of knowledge appears to be in the 2–100 μm size range which is too large to have been studied by colloid chemists and too small to be visible to the naked eye. It is suggested that more observations of soil structure should be made in this size range, as it may hold many important clues on how to manage soil structure in the field.